HONG KONG (Reuters) - Asia’s record number of teams preparing for the World Cup have found themselves increasingly challenged by poor results amid several coaching changes ahead of the finals in Russia.

Five nations will represent the Asian Football Confederation at this year’s tournament, the first time that many countries from the region have qualified for the World Cup.

But only one of the Asian teams will travel to the June 14-July 15 finals with the coach who was at the helm a year ago.

Carlos Queiroz’s tempestuous seven-year reign with Iran has been serene compared to that of his counterparts in Japan, South Korea, Saudi Arabia and Australia, with those countries heading to Russia with uncertainty clouding their potential progress.

The decision by the Japan FA to replace Bosnian Vahid Halilhodzic with Akira Nishino last week followed in the wake of Ange Postecoglou’s decision to resign as Australia coach and Dutchman Bert van Marwijk’s departure from Saudi Arabia.

The Koreans, meanwhile, fired Uli Stielike last June after a loss to Qatar put the country’s hopes of a ninth straight appearance at the World Cup in jeopardy.

The German’s replacement, Asian Champions League-winning coach Shin Tae-yong, has at least been given time to fashion his own team.

Steering the nation to a pair of scoreless draws against Iran and Uzbekistan ensured the Koreans qualified for the finals, allowing Shin the chance to build towards Russia.

Not that their progress has been entirely smooth.

After winning an East Asian Championship in Japan in December that did not feature any of the region’s Europe-based player, Shin’s side suffered back-to-back defeats against Northern Ireland and Poland last month.

SAUDI PROBLEMS

Saudi Arabia’s preparations have been even more fraught, with van Marwijk’s initial replacement Edgardo Bauza fired after three games, to be replaced with Juan Antonio Pizzi.

Pizzi, too, has had problems. Any encouragement from a 1-1 draw with Ukraine was dashed by Roberto Martinez’s Belgium side who thrashed the Saudis 4-0 with Romelu Lukaku scoring twice.

While Saudi Arabia stumble towards the World Cup’s opening game against hosts Russia, their ex-coach van Marwijk has been parachuted into Postecoglou’s old position with the Socceroos.

Given barely three months to fine-tune an Australia team that struggled in the latter stages of qualifying, he oversaw an encouraging 0-0 draw with Colombia last month after a 4-1 debut thrashing against a Norway side who failed to reach the finals.

Nishino, meanwhile, will be hard pressed to lift the mood of a Japan camp that has been battered in recent months.

A record 4-1 loss by South Korea in December could have been dismissed as inconsequential had Halilhodzic steered the team to positive results against Mali and Ukraine last month.

But a draw with the African side was followed by a loss to the Ukrainians, prompting the normally conservative JFA to fire a coach who had been under pressure for much of the last year.

“I want to get results,” Nishino said at his unveiling on Thursday. “It’s the World Cup, so I want us to show that we are good enough to get to the knockout round.

“But first of all I want the players to perform in the way that they are capable of. I want to bring that out of them.

“We have the players with the spirit to do that.”

Iran, the region’s highest ranked nation at number 36, appear to be Asia’s best hope for success in Russia, despite being drawn to face Spain, European champions Portugal and Morocco in the group phase.

But with Queiroz’s tumultuous relationship with the Iranian authorities a constant source of conflict, the experienced Portuguese coach could still face testing times ahead.